A Worm is a virus-like software application which spreads itself to other computers. Worms send themselves out to email addresses collected from the infected PC. Worms are known to mutate and they usually carry a destructive payload.

An apparently useful and innocent program containing additional hidden code which allows the unauthorized collection, exploitation, falsification, or destruction of data. When this program executes, the program performs a specific set of actions, usually working toward the goal of allowing the trojan to survive on a system and open up a backdoor.